A variety of protocols can be used to access files in a file system. These include the Apple Filing Protocol (AFP), the Common Internet File System (CIFS), and the Network Control Program (NCP) protocols. Indeed, each application running on a standalone machine, or within a network may use a separate protocol to access files.
When file locking is implemented between applications that access the files in a file system, and the access is accomplished using different protocols, there is currently no unified mechanism that can be used to inform one application that a particular file has been locked by another. In some cases, individual communication channels are opened between applications to communicate such information, so that the number of channels opened increases at least in proportion to the number of applications.